When you are talking with someone you know really well, that you talk to often, try each time to notice something about them that you have not noticed before: their appearance, manner of speaking, apparent state of mind, interests, anything. Talk to them about it or, if that is too much of a leap, write about it in your journal – but talk to them later.
Now, think of someone you see regularly but do not speak to: write their name in your journal. Commit to speaking to them sometime in the next seven days. Write that commitment down in your journal too. When you speak to them, notice at least three things about them you have not noticed before, three things that make them interesting. You might even use these as an opening for your conversation.